Add option to read ROM layout from IFD

Add an option --ifd to read the ROM layout from an Intel Firmware
Descriptor (IFD). Works the same as the -l option, if given, -i
specifies the images to update.

v2: o Rebased on libflashrom, use libflashrom interface.
    o Use functions from ich_descriptors.c.

v3: o Move ich_descriptors.o to LIB_OBJS, thus build it independent
      of arch and programmers.
    o Bail out if we aren't compiled for little endian.
    o Update flashrom.8.tmpl.

v4: o Incorporated David's comments.
    o Removed single-character `-d` option.

v5: Changed region names to match the output of `ifdtool --layout ...`

Change-Id: Ifafff2bf6d5c5e62283416b3269723f81fdc0fa3
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/17953
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

ich_descriptors.h

@@ -584,4 +584,6 @@ int read_ich_descriptors_from_dump(const uint32_t *dump, unsigned int len, struc
 int read_ich_descriptors_via_fdo(void *spibar, struct ich_descriptors *desc);
 int getFCBA_component_density(enum ich_chipset cs, const struct ich_descriptors *desc, uint8_t idx);
 
+int layout_from_ich_descriptors(struct ich_layout *, const void *dump, size_t len);
+
 #endif /* __ICH_DESCRIPTORS_H__ */